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How many friends can one person have?

Posted by Christopher Shea  October 8, 2010 11:31 AM

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A glance at some people's Facebook friends lists can make one feel like a loner. Assiduous networkers often have many hundreds or even thousands of "friends." But could all of those people possibly be worthy of the title?

Certainly not, according to the anthropologist and evolutionary biologist Robin Dunbar. In his work, Dunbar has actually proposed a number that, he thinks, represents the upper limit of rich human relationships any one person can sustain: 150.

Dunbar came up with that figure by looking at the size of the social networks maintained by other primates, and relating that number to brain size. Then he extrapolated outward to human brain mass. (The fact that we live in cities disguises our actual capacity for social interaction, which was formed in a primitive, rural environment, he argues.)

Brain-size correlation aside, groups of 150 are quite common in human societies, Dunbar has argued. The typical Army "company" has long contained 130-150 men, for example, as did neolithic villages in the Middle East.

And, in fact, the average person on Facebook has about that many friends.

(Dunbar's latest book is called, aptly enough, "How Many Friends Does One Person Need?" The publisher is Harvard University Press, whose blog recently discussed "Dunbar's number.")


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About brainiac Brainiac is the daily blog of the Globe's Sunday Ideas section, covering news and delights from the worlds of art, science, literature, history, design, and more. You can follow us on Twitter @GlobeIdeas.
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Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.


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